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Tech Talk: Snap’s Micro Gimbal

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When we decided to build Snap three years ago, our goal was to create a flying camera that wouldn’t just be lightweight and easy-to-use, but it would also capture professional-quality footage rivaling professional set ups. To accomplish this, we knew Snap would need gimbal stabilization.

A  gimbal-stabilized camera is mounted on actuators that move to keep the camera at a consistent orientation relative to the ground. Since Snap (and all other quadrotors) need to tilt quickly in order to move and maintain position, this stabilization of the camera is crucial for achieving smooth video.

The Problem: While gimbal stabilization is the standard for professional aerial video, most gimbals on the market weigh in at a 100 grams or more. Bigger gimbals are easier to hold steady—think about how it’s easier to balance a yardstick on your finger than a pencil. We needed one that was substantially lighter and smaller to comply with the lightweight and packable design we had imagined for Snap.

The Solution: After three years of intense R&D with a highly-talented team, our fair share of trial and error, and excessive amounts of coffee, we managed to engineer this impossible gimbal.  Check out the clip below—and keep your eye on the camera— to see Snap’s gimbal in action.

Even though this video was shot with one of Snap’s early prototypes, you can still get a sense for how the system works. Snap’s gimbal stabilization will also ensure that the vibrations from the propellers don’t distort the video, giving it that “jell-o” effect.

How’d we do it? Without giving away too much, here are some of our design secrets:

  • We integrated all of the gimbal components into the fewest possible parts. This enables us to create the stiffest possible assembly with minimal weight.
  • We designed our gimbal with materials and shapes that optimize strength-to-weight and stiffness-to-weight ratios. Strong and stiff equals precise, high-quality video.
  • We rotate the camera using custom-integrated low cogging torque motors to enable consistent, buttery-smooth rotation. The roll-stage motor is integrated into a one-piece cnc’d 6061 T6 aluminum yoke and holds the camera from both sides, making it both extremely stiff (remember, stiff = high video quality) and light, as well as extremely hard to break.
  • In the event that you do manage to destroy the gimbal, the entire assembly can be removed for repair by taking out two 2-mm allen-head screws.
  • In order to further reduce weight, we designed out the yaw axis on our gimbal. We did this by modifying the orientation of the blades on Snap to radically improve our level of yaw control and then adding custom Electronic Image Stabilization (EIS) to remove the sub-1 degree yaw movements to maintain pixel perfection.

As the gimbal gets smaller and lighter, little things like bearing drag and wire stiffness start to become big issues. Here’s how we tackled those:

  • We fabricated all the parts to absurdly high CNC machined tolerances, used the best quality bearings, created custom, ultra-flexible flex circuits, and used precise miniature hollow shafts for torque-free micro wire routing. In short, these additions will keep everything perfectly smooth in this new micro size.
  • To deal with isolating the propeller vibration from the gimbal, we coupled the mass of the gimbal with the fuselage and battery and then vibrationally isolated this assembly from the propellers, using custom-tuned isolators. Since the whole system is substantially lighter, we need smaller, less powerful propellers, which produce less vibration, giving us a leg-up on heavier systems.

Just getting the mechanicals right still isn’t enough, most of the essential innovation is in the control electronics and software:

  • Our proprietary control software makes over 1000 adjustments per second to the gimbal’s angle (nearly 10 times for each rotation of the 7000 rpm propellers!) and can maintain less than 0.05 degrees of pointing accuracy.
  • In order to maintain the fastest possible response, our gimbal’s control software actually anticipates Snap’s movement through integration with the flight controller, so the gimbal can respond in perfect synchronicity with Snap’s movements (this is called “feed-forward,” in control-theory speak).

All of these design and engineering changes translate to a gimbal that can hold its own against the big boys. We can’t wait for you to try it out.

Leave your questions in the comments.

Best,

Tobin, Joe and the Vantage Robotics team